An aroma diffuser is an aromatherapy device. It typically atomizes water mixed with an essential oil by using high-frequency oscillation such as ultrasonic vibration and then diffusing it into the air to make the air full of fragrance.
The aroma diffuser typically supplies the essential oil by oil dripping. That is, the essential oil is dripped into the water all at once. Because it has a density lower than that of water, the essential oil would float on the water surface after being dripped into a tank of the aroma diffuser. As such, when the aroma diffuser is operating, the essential oil concentration in the tank would decrease as the time of operation progresses, because the essential oil and water are atomized and diffused simultaneously. Therefore, the fragrance of the atomized vapor would become increasingly light, resulting in an unsatisfactory user experience.